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<h1><a name="SECTION0018100000000000000000">
16.1 <tt class="module">posix</tt> --
         The most common POSIX system calls</a>
</h1>

<p>
<a name="module-posix"></a>  
<p class="availability">Availability: <span
 class="platform">Unix</span>.</p>

<p>
This module provides access to operating system functionality that is
standardized by the C Standard and the POSIX standard (a thinly
disguised <span class="Unix">Unix</span> interface).

<p>
<strong>Do not import this module directly.</strong>  Instead, import the
module <tt class="module"><a href="module-os.html">os</a></tt>, which provides a <em>portable</em> version of this
interface.  On <span class="Unix">Unix</span>, the <tt class="module"><a href="module-os.html">os</a></tt> module provides a superset of
the <tt class="module">posix</tt> interface.  On non-<span class="Unix">Unix</span> operating systems the
<tt class="module">posix</tt> module is not available, but a subset is always
available through the <tt class="module"><a href="module-os.html">os</a></tt> interface.  Once <tt class="module"><a href="module-os.html">os</a></tt> is
imported, there is <em>no</em> performance penalty in using it instead
of <tt class="module">posix</tt>.  In addition, <tt class="module"><a href="module-os.html">os</a></tt><a id='l2h-3513' xml:id='l2h-3513'></a>
provides some additional functionality, such as automatically calling
<tt class="function">putenv()</tt> when an entry in <code>os.environ</code> is changed.

<p>
The descriptions below are very terse; refer to the corresponding
<span class="Unix">Unix</span> manual (or POSIX documentation) entry for more information.
Arguments called <var>path</var> refer to a pathname given as a string.

<p>
Errors are reported as exceptions; the usual exceptions are given for
type errors, while errors reported by the system calls raise
<tt class="exception">error</tt> (a synonym for the standard exception
<tt class="exception">OSError</tt>), described below.

<p>

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<li><a href="posix-large-files.html">16.1.1 Large File Support</a>
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